Method for multicast transmission based on channel feedback

ABSTRACT

A method of receiving multicast transmission from a base station includes receiving allocation information about a feedback channel including a plurality of resources shared by another terminal, determining feedback information based on an estimated channel with the base station, determining a plurality of transmission power levels respectively corresponding to the plurality of resources based on the feedback information, and transmitting channel feedback to the base station on the feedback channel based on the plurality of transmission power levels.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.16,747,956, filed on Jan. 21, 2020, which claims the benefit of KoreanPatent Application No. 10-2019-0088524, filed on Jul. 22, 2019, in theKorean Intellectual Property Office, the entire disclosure of each ofwhich is incorporated herein in its entirety by reference.

BACKGROUND

Example embodiments of the inventive concepts relate to wirelesscommunication. For example, at least some example embodiments relate toa method and/or apparatus for multicast transmission based on channelfeedback.

Multicast may denote group communication for transmitting data to aplurality of devices included in the same group. For example, multicastin wireless communication may denote that a base station communicateswith a plurality of terminals included in the same group (or a multicastgroup) in common. In order for the plurality of terminals of themulticast group to validly receive multicast transmission, the basestation may determine transmission parameters for the multicasttransmission. For example, the transmission parameters may be determinedbased on conditions of a plurality of channels between the base stationand the plurality of terminals, and the conditions of the plurality ofchannels may be obtained from channel feedbacks provided from theplurality of terminals. Also, even when a new terminal subscribes to amulticast group or an existing terminal cancels a subscription to themulticast group, the base station may determine transmission parametersagain. Therefore, overhead for determining a transmission parameter mayaffect the efficiency of multicast transmission.

SUMMARY

Example embodiments of the inventive concepts provide a method and/orapparatus for multicast transmission based on efficient channel feedbackin wireless communication.

According to an example embodiment of the inventive concepts, there isprovided a method of operating a terminal to receive multicasttransmission from a base station, the method including receivingallocation information associated with a feedback channel, the feedbackchannel including a plurality of resources shared with another terminal;determining feedback information based on an estimated channel with thebase station; determining, based on the feedback information, aplurality of transmission power levels corresponding to the plurality ofresources shared with the another terminal, respectively; transmittingchannel feedback to the base station on the feedback channel, thechannel feedback based on the plurality of transmission power levels;and receiving the multicast transmission from the base station, thechannel feedback being utilized by the base station to provide themulticast transmission to the terminal and the another terminal.

According to another example embodiment of the inventive concepts, thereis provided a method of operating a terminal to provide a base stationwith channel feedback for multicast transmission, the method includingreceiving allocation information associated with a feedback channel, thefeedback channel including M resources shared with another terminal,wherein M is an integer of more than 1; determining feedback informationbased on an estimated channel with the base station; encoding thefeedback information as an M-bit string; setting, based on the M-bitstring, a transmission power level of respective ones of the M resourcesas a first transmission power level or a second transmission powerlevel; and transmitting channel feedback to the base station on thefeedback channel based on the transmission power level of each of the Mresources, the channel feedback being utilized by the base station toprovide the multicast transmission to the terminal and the anotherterminal.

According to another example embodiment of the inventive concepts, thereis provided a method of providing multicast transmission to a pluralityof terminals, the method including providing the plurality of terminalswith allocation information associated with a feedback channel, thefeedback channel including a plurality of resources shared with theplurality of terminals; simultaneously receiving, over the feedbackchannel, a plurality of channel feedbacks from the plurality ofterminals; determining a transmission parameter based on a plurality ofreception power accumulated in the plurality of resources using theplurality of channel feedbacks; and providing the multicast transmissionto the plurality of terminals based on the transmission parameter.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments of the inventive concepts will be more clearlyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 is a diagram illustrating a wireless communication systemaccording to an example embodiment;

FIG. 2 is a flowchart illustrating a method for multicast transmissionaccording to an example embodiment;

FIGS. 3A and 3B are diagrams illustrating examples of a feedback channelaccording to an example embodiment;

FIG. 4 is a diagram illustrating an example of combined channel feedbackaccording to an example embodiment;

FIGS. 5A and 5B are tables applied to a wireless communication systemaccording to embodiments;

FIG. 6 is a flowchart illustrating a method for multicast transmissionaccording to an example embodiment;

FIGS. 7A and 7B are tables showing examples of transmission power levelsof resources corresponding to feedback information according toembodiments;

FIGS. 8A and 8B are tables showing examples of transmission power levelsof resources corresponding to feedback information according toembodiments;

FIG. 9 is a diagram illustrating an example of channels formed by a basestation and a plurality of terminals included in one multicast groupaccording to an example embodiment;

FIG. 10 is a flowchart illustrating a method for multicast transmissionaccording to an example embodiment;

FIGS. 11A and 11B are graphs showing examples of combined channelfeedback obtained by a base station according to an example embodiment;

FIGS. 12A and 12B are graphs showing examples of combined channelfeedback obtained by a base station according to an example embodiment;

FIG. 13 is a diagram illustrating a wireless communication systemaccording to an example embodiment;

FIG. 14 is a diagram illustrating a physical time-frequency structurefor feedback channels according to an example embodiment;

FIG. 15 is a block diagram illustrating a wireless communicationapparatus according to an example embodiment; and

FIG. 16 is a block diagram illustrating a signal processor according toan example embodiment.

DETAILED DESCRIPTION

FIG. 1 is a diagram illustrating a wireless communication system 10according to an example embodiment.

Referring to FIG. 1 , the wireless communication system 10 may include abase station 12 and a multicast group 14.

As a non-limiting example, the wireless communication system 10 may be awireless communication system using a cellular network such as a 5^(th)generation (5G) wireless system, a long term evolution (LTE) system, anLTE-advanced system, a code division multiple access (CDMA) system, aglobal system for mobile communication (GSM) system, or may be awireless personal area network (WPAN) system or another arbitrarywireless communication system. Hereinafter, an example where thewireless communication system 10 uses a cellular network will be mainlydescribed, but it may be understood that example embodiments are notlimited thereto.

The wireless communication system 10 may support unicast, multicast,and/or broadcast, and particularly, the wireless communication system 10for supporting multicast and broadcast may be referred to as supportingmulticast/broadcast services or multimedia broadcast multicast services(MBMS). For example, unicast transmission may denote transmissionprovided from a base station 12 to a terminal (for example, 14_1),multicast transmission may denote transmission provided from the basestation 12 to a plurality of terminals of one group (i.e., a multicastgroup (for example, 14)), and broadcast transmission may denotetransmission provided from the base station 12 to a plurality ofterminals of a multicast group (for example, 14) and a plurality ofterminals of another multicast group.

Unicast transmission may be provided based on transmission parameterswhich are determined to ensure valid reception by a terminal. On theother hand, in a multicast/broadcast service, transmission may beprovided based on transmission parameters which are determined to ensurevalid receptions by a plurality of terminals, and thus, transmissionparameters (for example, a modulation order, a code rate, etc.) may bedetermined based on a worst channel among channels associated with aplurality of terminals. In the multicast/broadcast service, a pluralityof channel conditions formed by the base station 12 and a plurality ofterminals may differ and may be frequently changed. Conventionally, itmay be difficult for a base station to efficiently obtain the pluralityof channel conditions, thus increasing overhead for determiningtransmission parameters and reducing the efficiency of themulticast/broadcast service.

In contrast, in one or more example embodiments, the base station 12, asdescribed below with reference to the drawings, may simultaneouslyobtain a plurality of channel conditions, used for determination oftransmission parameters in the multicast/broadcast service, on afeedback channel shared by a plurality of terminals, instead ofobtaining the channel conditions from the plurality of terminals and mayobtain a worst channel condition (i.e., a lowest channel condition).Therefore, the efficiency of the multicast/broadcast service may beconsiderably enhanced, and particularly, transmission parameters formulticast transmission MC may be determined within a certain timeregardless of a variation of the number of terminals included in amulticast group 14, which receives the multicast transmission MC.

Hereinafter, in example embodiments, multicast transmission will bemainly described, but it may be understood that example embodimentsapply to broadcast transmission. Also, in embodiments, an example wherea base station provides multicast transmission to a plurality ofterminals will be mainly described, but it may be understood thatexample embodiments apply to multicast transmission provided from oneterminal to other terminals.

The base station 12 may denote a fixed station which communicates with aterminal and/or another base station generally, and by communicatingwith a terminal and/or another base station, the base station 12 mayexchange data and control information and may be referred to as anetwork access device. For example, the base station 12 may be referredto as a Node B, an evolved-Node B (eNB), a next generation Node B (gNB),a sector, a site, a base transceiver system (BTS), an access point (AP),a relay node, a remote radio head (RRH), a radio unit (RU), or a smallcell. Herein, a base station or a cell may be construed as acomprehensive meaning which represents a function or a certain areacovered by a base station controller (BSC) in CDMA, a Node-B in WCDMA,an eNB in LTE, or a 5G gNB or sector (site), and may include variouscoverage areas such as a communication range of each of a mega cell, amacro cell, a micro cell, a pico cell, a Femto cell, a relay node, anRRH, an RU, and a small cell.

The terminal (for example, 14_1) may be a wireless communicationapparatus, and may be stationary or mobile and may denote an arbitrarydevice for transmitting and receiving data and/or control information byperforming wireless communication with the base station 12. For example,a terminal may be referred to as user equipment (UE), terminalequipment, a mobile station (MS), a mobile terminal (MT), a userterminal (UT), a subscriber station (SS), a wireless device, or ahandheld device.

The multicast group 14 may include first to p^(th) terminals 14_1 to14_p (where p is an integer of more than 1), and the first to p^(th)terminals 14_1 to 14_p may receive the multicast transmission MC fromthe base station 12. The base station 12 may receive first to p^(th)channel feedbacks CF1 to CFp respectively from the first to p^(th)terminals 14_1 to 14_p, for determining transmission parameters for themulticast transmission MC. For example, as illustrated in FIG. 1 , thefirst terminal 14_1 may provide the first channel feedback CF1 to thebase station 12, the second terminal 14_2 may provide the second channelfeedback CF2 to the base station 12, and the p^(th) terminal 14_p mayprovide the p^(th) channel feedback CFp to the base station 12.

The first to p^(th) channel feedbacks CF1 to CFp may be transmitted tothe base station 12 on a feedback channel shared by the first to p^(th)terminals 14_1 to 14_p. For example, the first terminal 14_1 maydetermine feedback information based on a channel estimated based on thebase station 12 and may control transmission power levels of resourcesincluded in a feedback channel so that the first channel feedback CF1represents the determined feedback information. Similarly, each of thesecond to p^(th) terminals 14_2 to 14_p may control transmission powerlevels of resources included in a feedback channel based on feedbackinformation. The base station 12 may receive combined channel feedback(for example, CFs of FIG. 4 ) from the first to p^(th) terminals 14_1 to14_p and may determine the transmission parameters for the multicasttransmission MC based on the combined channel feedback. For example, thebase station 12 may determine a lowest channel condition (i.e., acondition of a worst channel) among conditions of channels between thebase station 12 and the first to p^(th) terminals 14_1 to 14_p based onthe combined channel feedback and may determine transmission parametersbased on the lowest channel condition. Examples of the combined channelfeedback will be described below with reference to FIGS. 4, 11A, 11B,12A, and 12B.

FIG. 2 is a flowchart illustrating a method for multicast transmissionaccording to an example embodiment. In detail, the flowchart of FIG. 2may represent operations of a base station 22 and a terminal 24 overtime. In some example embodiments, the base station 22 may be an exampleof the base station 12 of FIG. 1 , and the terminal 24 may be an exampleof a terminal included in the multicast group 14 of FIG. 1 .

Referring to FIG. 2 , in operation S10, the base station 22 may performan operation of allocating a feedback channel. For example, the basestation 22 may allocate a plurality of resources to a feedback channelfor receiving channel feedback. Herein, a resource may be a unit capableof being independently controlled by a wireless communication apparatus(i.e., the base station 22 or the terminal 24) and may be referred to asa time-frequency resource, and a feedback channel may include aplurality of resources which are successive in a time domain and/or afrequency domain Examples of a feedback channel will be described belowwith reference to FIGS. 3A and 3B. In some example embodiments, the basestation 22 may manage a plurality of multicast groups and may allocate aplurality of feedback channels to each of the plurality of multicastgroups. Examples where the base station 22 manages a plurality ofmulticast groups will be described below with reference to FIGS. 13 and14 .

In operation S20, the base station 22 may transmit allocationinformation about a feedback channel to the terminal 24. For example,multicast transmission may be provided on a multicast channel MCH, andthe multicast channel MCH may include a multicast traffic channel MTCHand a multicast control channel MCCH. In some example embodiments, thebase station 22 may provide the allocation information about thefeedback channel on the multicast control channel MCCH. The allocationinformation about the feedback channel may represent locations andconfigurations (for example, the number) of resources allocated to afeedback channel for a multicast group including the terminal 24, and inaddition to the terminal 24, other terminals included in the multicastgroup including the terminal 24 may receive the allocation informationabout the feedback channel from the base station 22.

In operation S30, the terminal 24 may determine channel estimationinformation and feedback information. For example, the terminal 24 mayestimate a channel (or a channel status or a channel condition) based onsignals (for example, reference signals) transmitted by the base station22. The terminal 24 may determine feedback information, which is to beprovided to the base station 22, based on the estimated channel, and forexample, the feedback information may include channel-status information(CSI). In some example embodiments, as described below with reference toFIG. 5A, feedback information may include channel quality indication(CQI). In some example embodiments, as described below with reference toFIG. 5B, feedback information may include a modulation coding scheme(MCS). Also, in some example embodiments, feedback information mayinclude a rank indicator (RI) and precoder matrix indication (PMI).

In operation S40, the terminal 24 may determine a transmission powerlevel of each of resources included in the feedback channel. Theterminal 24 may control the transmission power levels of the resourcesincluded in the feedback channel, for representing at least a portion ofthe feedback information which is determined in operation S30. To thisend, when the feedback channel includes M (where M is an integer of morethan 1) resources, the terminal 24 may encode the feedback informationas an M-bit string and may determine transmission power levels of the Mresources based on the encoded M-bit string. Each of the terminalsincluded in the multicast group may encode feedback informationaccording to the same encoding scheme. In some example embodiments, inoperation S20, the base station 22 may transmit allocation informationabout a feedback channel, including an encoding scheme, to the terminal24. Therefore, the terminal 24 may extract an encoding scheme from theallocation information about the feedback channel and may encode thefeedback information according to the extracted encoding scheme. Asdescribed below with reference to FIGS. 7A, 7B, 8A, and 8B, an encodingscheme which enables the base station 22 to obtain combined feedbackinformation based on accumulated reception power of resources includedin a feedback channel may be adopted. Examples of operation S40 will bedescribed below with reference to FIGS. 6 and 10 .

In operation S50, the terminal 24 may transmit the feedback informationto the base station 22 on the feedback channel That is, the terminal 24may transmit channel feedback to the base station 22. For example, theterminal 24 may transmit the feedback information to the base station 22on the feedback channel based on the transmission power levels which aredetermined in operation S40, and the feedback information may berepresented by a combination of transmission power of resources includedin the feedback channel.

In operation S60, the base station 22 may determine transmissionparameters. The base station 22 may receive combined channel feedbackfrom channel feedbacks transmitted by a plurality of terminals includingthe terminal 24 and may determine the transmission parameters based onthe combined channel feedback. For example, the base station 22 maydetect a lowest channel condition from among channel conditions based onthe terminals included in the multicast group, based on the combinedchannel feedback and may determine transmission parameters (for example,a modulation order, a code rate, etc.) corresponding to the lowestchannel condition.

In operation S70, the base station 22 may provide multicasttransmission. For example, the base station 22 may provide the multicasttransmission to the terminal 24 and other terminals each included in themulticast group based on the transmission parameters which aredetermined in operation S60. Therefore, all terminals included in themulticast group may validly receive the multicast transmission.

FIGS. 3A and 3B are diagrams illustrating examples of a feedback channelaccording to an example embodiment. In detail, FIG. 3A illustratesavailable channel feedback CFa in a feedback channel FCa including aplurality of resources divided in a time domain, and FIG. 3B illustratesavailable channel feedback CFb in a feedback channel FCb including aplurality of resources divided in a frequency domain. As described abovewith reference to FIGS. 1 and 2 , the feedback channel FCa of FIG. 3A orthe feedback channel FCb of FIG. 3B may be shared by terminals includedin the same multicast group. Hereinafter, a repetitive description amongdescriptions of FIGS. 3A and 3B will be omitted.

Referring to FIG. 3A, the feedback channel FCa may include first toM^(th) (where M is an integer of more than 1) resources R1 to RM dividedin the time domain. As illustrated in FIG. 3A, the first to M^(th)resources R1 to RM may each have a certain width in a frequency axis andmay be continuously disposed in a time axis. Each of the first to M^(th)resources R1 to RM may have a first transmission power level L1 or asecond transmission power level L2 based on feedback information. Forexample, as illustrated in FIG. 3A, in the channel feedback CFa, thesecond resource R2 may have the first transmission power level L1, whichis higher than the second transmission power level L2, and the otherresources including the first, third, and M^(th) resources R1, R3, andRM may have the second transmission power level L2. The channel feedbackCFa may be expressed as an M-bit string ‘010 . . . 0’. Herein, it may beassumed that the second transmission power level L2 is zero and thefirst transmission power level L1 is higher than the second transmissionpower level L2.

Referring to FIG. 3B, the feedback channel FCb may include first toM^(th) (where M is an integer of more than 1) resources R1 to RM dividedin the frequency domain. As illustrated in FIG. 3B, the first to M^(th)resources R1 to RM may each have a certain width in a time axis and maybe continuously disposed in a frequency axis. Each of the first toM^(th) resources R1 to RM may have a first transmission power level L1or a second transmission power level L2 based on feedback information.For example, as illustrated in FIG. 3B, in the channel feedback CFb, thefirst resource R1 may have the first transmission power level L1, andthe other resources including the second, third, and M^(th) resourcesR2, R3, and RM may have the second transmission power level L2. Thechannel feedback CFb may be expressed as an M-bit string ‘100 . . . 0’.

FIG. 4 is a diagram illustrating an example of combined channel feedbackaccording to an example embodiment. In detail, FIG. 4 illustrates anexample where the base station 12 of FIG. 1 receives combined channelfeedback CFs from the first to p^(th) terminals 14_1 to 14_p included inthe multicast group 14. In FIG. 4 , it may be assumed that a feedbackchannel includes eight resources. Hereinafter, FIG. 4 will be describedwith reference to FIG. 1 .

Each of the first to p^(th) terminals 14_1 to 14_p included in themulticast group 14 may transmit channel feedback to the base station 12based on feedback information, and the feedback information mayrepresent that an estimated channel is poor as an index of a resource,having a first transmission power level, of the first to eighthresources R1 to R8 decreases. For example, as illustrated in FIG. 4 ,when the third resource R3 has the first transmission power level in afirst channel feedback CF1 and the fifth resource R5 has the firsttransmission power level in a second channel feedback CF2, this mayrepresent that a channel condition between the base station 12 and thefirst terminal 14_1 is worse than a channel condition between the basestation 12 and the second terminal 14_2.

In the combined channel feedback CFs, due to first to p^(th) channelfeedbacks CF1 to CFp, the first to eighth resources R1 to R8 may haveaccumulated reception power as illustrated in FIG. 4 . As describedabove with reference to FIGS. 1 and 2 , in order to detect a lowestchannel condition from among conditions of a plurality of channels, thebase station 12 may detect a resource corresponding to a minimum indexfrom among resources having a reception power level which is equal to orhigher than the first transmission power level. For example, asillustrated in FIG. 4 , in any channel feedback of the first to p^(th)channel feedbacks CF1 to CFp, the first resource R1 or the secondresource R2 may not have the first transmission power level, and thus,the base station 12 may detect the third resource R3 and may detect alowest channel condition corresponding to the third resource R3. Thefirst to p^(th) channel feedbacks CF1 to CFp may be generated based onone-hot encoding, and as described below with reference to FIGS. 7B, 8A,and 8B, in some example embodiments, channel feedback may be generatedbased on an encoding scheme differing from the illustration of FIG. 4 ,whereby the lowest channel condition may be detected based on differentencoding schemes.

Although it is illustrated in FIG. 4 that the first transmission powerlevels output from the first to p^(th) terminals 14_1 to 14_p areaccumulated in the combined channel feedback CFs for convenience ofillustration, a reception power level transferred to the base station 12may differ from a level obtained by accumulating the first transmissionpower level, due to channels between the base station 12 and the firstto p^(th) terminals 14_1 to 14_p. Also, despite different conditions ofchannels, the first transmission power level of each of the first top^(th) terminals 14_1 to 14_p may be received by the base station 12 asa reception power level having the same level, in order for the basestation 12 to detect a lowest channel condition. Therefore, each of thefirst to p^(th) terminals 14_1 to 14_p may determine the firsttransmission power level based on a channel condition, and thus, thefirst transmission power level may differ for each of the first top^(th) terminals 14_1 to 14_p. An operation of determining, by using aterminal, the first transmission power level will be described belowwith reference to FIGS. 9 and 10 .

FIGS. 5A and 5B are tables applied to a wireless communication systemaccording to embodiments. In detail, FIG. 5A shows one CQI table T_CQIof CQI tables prescribed in 5G NR, and FIG. 5B shows one MCS table T_MCSof MCS tables prescribed in 5G NR. Hereinafter, FIGS. 5A and 5B will bedescribed with reference to FIGS. 2 and 4 .

Referring to FIG. 5A, in some example embodiments, feedback informationmay include a CQI index. As illustrated in FIG. 5A, the CQI index maydefine a modulation order and a code rate, and a relatively high CQIindex may correspond to a relatively high modulation order and coderate. The terminal 24 may transmit the CQI index, corresponding to amaximally supportable modulation order and code rate, as the feedbackinformation to the base station 22 on a feedback channel based on anestimated channel, and the base station 12 may detect a minimum CQIindex from among CQI indexes received from a plurality of terminalsincluding the terminal 24 to detect a lowest channel condition. Asillustrated in FIG. 5A, in the CQI table T_CQI, the CQI index may haveone value among sixteen different values, and thus, as described belowwith reference to FIGS. 7A, 7B, 8A, and 8B, when the feedbackinformation includes the CQI index, a feedback channel may includesixteen resources for representing the CQI index.

Referring to FIG. 5B, in some example embodiments, feedback informationmay include an MCS index. As illustrated in FIG. 5B, the MCS index maydefine a modulation order and a target code rate, and a relatively highMCS index may correspond to a relatively high modulation order andtarget code rate. The terminal 24 may transmit the MCS index,corresponding to a maximally supportable modulation order and targetcode rate, as the feedback information to the base station 22 on afeedback channel based on an estimated channel, and the base station 12may detect a minimum MCS index from among MCS indexes received from aplurality of terminals including the terminal 24 to detect a lowestchannel condition. As illustrated in FIG. 5B, in the MCS table T_MCS,the MCS index may have one value among thirty-two different values, andthus, when the feedback information includes the MCS index, a feedbackchannel may include thirty-two resources for representing the MCS index.Hereinafter, the CQI index will be described as feedback information,but it may be understood that example embodiments are not limitedthereto.

FIG. 6 is a flowchart illustrating a method for multicast transmissionaccording to an example embodiment. In detail, the flowchart of FIG. 6represents an example of operation S40 of FIG. 2 . As described abovewith reference to FIG. 2 , in operation S40′ of FIG. 6 , an operation ofdetermining a transmission power level of each of resources included ina feedback channel may be performed, and as illustrated in FIG. 6 ,operation S40′ may include operation S42 and operation S44. In someexample embodiments, operation S40′ may be performed by the terminal 24of FIG. 2 . Hereinafter, FIG. 6 will be described with reference to FIG.2 .

Referring to FIG. 6 , in operation S42, an operation of encodingfeedback information as an M-bit string may be performed. M may bedetermined based on the number of values of the feedback information,and bits of the M-bit string may respectively correspond to M resourcesincluded in the feedback channel. For example, M may be 16, forrepresenting the sixteen CQI indexes included in the CQI table T_CQI ofFIG. 5A. In some example embodiments, as described below with referenceto FIGS. 7A and 7B, the feedback information may be encoded as the M-bitstring based on one-hot encoding or one-cold encoding. Moreover, in someexample embodiments, as described below with reference to FIGS. 8A and8B, the feedback information may be encoded as the M-bit string based onunary coding.

In operation S44, an operation of determining a transmission power levelof each of the M resources as a first transmission power level or asecond transmission power level may be performed. For example, theterminal 24 may determine the transmission power level of each of the Mresources included in the feedback channel based on the M-bit stringobtained through encoding which is performed in operation S42. Herein,it may be assumed that a resource corresponding to a bit ‘1’ of theM-bit string is determined to have the first transmission power leveland a resource corresponding to a bit ‘0’ of the M-bit string isdetermined to have the second transmission power level.

In some example embodiments, in a case where the M-bit string is encodedbased on one-hot encoding, as described below with reference to FIG. 7A,one of a plurality of resources may have the first transmission powerlevel based on the feedback information. Also, in some exampleembodiments, in a case where the M-bit string is encoded based onone-cold encoding, as described below with reference to FIG. 7B, one ofa plurality of resources may have the second transmission power levelbased on the feedback information.

In some example embodiments, in a case where the M-bit string is encodedbased on unary coding, as described below with reference to FIGS. 8A and8B, at least one successive resource of a plurality of resources mayhave the first transmission power level or the second transmission powerlevel based on the feedback information. In some example embodiments,the at least one resource having the first transmission power level orthe second transmission power level may include a first resource (forexample, R1 of FIG. 4 ) of the plurality of resources, and in some otherexample embodiments, may include a last resource (for example, R8 ofFIG. 4 ) of the plurality of resources.

FIGS. 7A and 7B are tables showing examples of transmission power levelsof resources corresponding to feedback information according toembodiments. In detail, a table of FIG. 7A may represent transmissionpower levels of resources corresponding to bit strings which areobtained by encoding the CQI indexes defined in the CQI table T_CQI ofFIG. 5A based on one-hot encoding, and a table of FIG. 7B may representtransmission power levels of resources corresponding to bit stringswhich are obtained by encoding the CQI indexes defined in the CQI tableT_CQI of FIG. 5A based on one-cold encoding. In FIGS. 7A and 7B, aresource having a first transmission power level may be shaded, and aresource having a second transmission power level may not be shaded.

Referring to FIG. 7A, the CQI index may be encoded as a 16-bit stringbased on one-hot encoding. For example, CQI indexes 1 0, 1, . . . , 14,and 15’ may be respectively encoded as 16-bit strings ‘1000000000000000,0100000000000000, . . . , 0000000000000010, and 0000000000000001’.Therefore, a transmission power level of each of sixteen resources maybe determined as illustrated in FIG. 7A. In some example embodiments,unlike the illustration of FIG. 7A, CQI indexes ‘0, 1, . . . , 14, and15’ may be respectively encoded as 16-bit strings ‘0000000000000001,0000000000000010, . . . , 0100000000000000, and 1000000000000000’ basedon one-hot encoding.

Referring to FIG. 7B, the CQI index may be encoded as a 16-bit stringbased on one-cold encoding. For example, the CQI indexes ‘0, 1, . . . ,14, and 15’ may be respectively encoded as 16-bit strings‘0111111111111111, 1011111111111111, . . . , 1111111111111101, and1111111111111110’. Therefore, a transmission power level of each ofsixteen resources may be determined as illustrated in FIG. 7B. In someexample embodiments, unlike the illustration of FIG. 7B, the CQI indexes‘0, 1, . . . , 14, and 15’ may be respectively encoded as 16-bit strings‘1111111111111110, 1111111111111101, . . . , 1011111111111111, and0111111111111111’ based on one-cold encoding.

FIGS. 8A and 8B are tables showing examples of transmission power levelsof resources corresponding to feedback information according to exampleembodiments. In detail, a table of FIG. 8A may represent transmissionpower levels of resources corresponding to bit strings which areobtained by encoding the CQI indexes defined in the CQI table T_CQI ofFIG. 5A based on unary encoding and of which the number of bits ‘1’increases as the CQI index increases, and a table of FIG. 8B mayrepresent transmission power levels of resources corresponding to bitstrings which are obtained by encoding the CQI indexes defined in theCQI table T_CQI of FIG. 5A based on unary encoding and of which thenumber of bits ‘0’ increases as the CQI index increases. In FIGS. 8A and8B, a resource having a first transmission power level may be shaded anda resource having a second transmission power level may not be shaded.FIGS. 8A and 8B show some examples of unary coding, and it may beunderstood that other examples (for example, a generalized unary code)of unary coding may be implemented.

Referring to FIG. 8A, the CQI index may be encoded as a 16-bit string ofwhich the number of bits ‘1’ increases as the CQI index increases basedon unary coding. For example, CQI indexes ‘0, 1, . . . , 14, and 15’ maybe respectively encoded as 16-bit strings ‘1000000000000000,1100000000000000, . . . , 1111111111111110, and 1111111111111111’.Therefore, a transmission power level of each of sixteen resources maybe determined as illustrated in FIG. 8A. Referring to FIG. 8B, the CQIindex may be encoded as a 16-bit string of which the number of bits ‘0’increases as the CQI index increases based on unary coding. For example,CQI indexes ‘0, 1, . . . , 14, and 15’ may be respectively encoded as16-bit strings ‘0111111111111111, 0011111111111111, . . . ,0000000000000001, and 0000000000000000’. Therefore, a transmission powerlevel of each of sixteen resources may be determined as illustrated inFIG. 8B. The above-described unary coding of FIGS. 8A and 8B may bereferred to as thermometer coding.

FIG. 9 is a diagram illustrating an example of channels formed by a basestation and a plurality of terminals included in one multicast groupaccording to an example embodiment. As illustrated in FIG. 9 , first tosixth terminals 94_1 to 94_6 included in the same multicast group 90 mayrespectively form first to sixth channels CH1 to CH6 along with a basestation 92.

Conditions of the first to sixth channels CH1 to CH6 may differ due tovarious factors. For example, the conditions of the first to sixthchannels CH1 to CH6 may depend on distances between the base station 92and the first to sixth terminals 94_1 to 94_6, interference betweenchannels, and obstacles between the base station 92 and the first tosixth terminals 94_1 to 94_6. Due to different channel conditions,transmission power output from the first to sixth terminals 94_1 to 94_6on a feedback channel may differently attenuated until reaching the basestation 92. It may be desirable that a transmission power level (i.e., afirst transmission power level) of a resource for representing feedbackinformation is received by the base station 92 at reception power havingthe same level as a level needed for the first to sixth terminals 94_1to 94_6 regardless of the first to sixth channels CH1 to CH6, and thus,each of the first to sixth terminals 94_1 to 94_6 may determine themagnitude of the first transmission power level based on the first tosixth channels CH1 to CH6. An operation of determining, by using aterminal, the magnitude of the first transmission power level will bedescribed below with reference to FIG. 10 . It may be desirable that asecond transmission power level is received by the base station 92 atreception power having the same level as a level needed for the first tosixth terminals 94_1 to 94_6 regardless of the first to sixth channelsCH1 to CH6, but for convenience of description, it may be assumed thatthe second transmission power level or a reception power level,corresponding to the second transmission power level, of the basestation 92 is zero.

FIG. 10 is a flowchart illustrating a method for multicast transmissionaccording to an example embodiment. In detail, the flowchart of FIG. 10represents operation S41 of performing an operation of determining themagnitude of a first transmission power level, and in some exampleembodiments, operation S41 of FIG. 10 may be included in operation S40of FIG. 2 . As illustrated in FIG. 10 , operation S41 may includeoperations S41_2 and S41_4. In some example embodiments, operation S41may be performed by the terminal 24 of FIG. 2 . Hereinafter, FIG. 10will be described with reference to FIG. 2 .

In operation S41_2, an operation of measuring reception power may beperformed. For example, the terminal 24 may measure the reception powerbased on transmission (for example, reference signals) provided by thebase station 22. When transmission power of the base station 22 is P_(T)and an estimated channel between the base station 22 and the terminal 24is h_(B), reception power P_(R) measured by the terminal 24 may beexpressed as the following Equation (1).

P _(R) =P _(T) |h _(B)|²   [Equation 1]

Reception power measured by terminals included in a multicast group maydiffer due to different channel conditions despite the same transmissionpower P_(T).

In operation S41_4, an operation of calculating the magnitude P of afirst transmission power level so as to be inversely proportional toreception power may be performed. For example, the magnitude P of thefirst transmission power level may be expressed as the followingEquation (2).

$\begin{matrix}{P = {\frac{\alpha}{P_{R}} = {\frac{\alpha}{P_{T}{❘h_{B}❘}^{2}} = {\frac{\gamma}{{❘h_{B}❘}^{2}}\left( {\gamma = \frac{\alpha}{P_{T}}} \right)}}}} & \left\lbrack {{Equation}2} \right\rbrack\end{matrix}$

In Equation (2), α may be determined based on a wireless communicationenvironment of each of the base station 22 and the terminal 24, and forexample, may be a value which is selected from among predefined valuesbased on path loss, shading, a multipath, and an ambient environment.

In some example embodiments, as described above with reference to FIG.7A, a CQI index may be encoded based on one-hot encoding, and in a casewhere the magnitude P of the first transmission power level iscalculated as in Equation (2), a transmission power level P_(m) of anm^(th) resource R_(m) in a feedback channel may be expressed as thefollowing Equation (3) (1≤m≤M).

$\begin{matrix}{P_{m} = \left\{ \begin{matrix}{{\frac{\gamma}{{❘h_{B}❘}^{2}}{for}m} = {{{CQI}{index}} + 1}} \\{0{otherwise}}\end{matrix} \right.} & \left\lbrack {{Equation}3} \right\rbrack\end{matrix}$

In some example embodiments, as described above with reference to FIG.7B, a CQI index may be encoded based on one-cold encoding, and in a casewhere the magnitude P of the first transmission power level iscalculated as in Equation (2), the transmission power level P_(m) of them^(th) resource R_(m) in the feedback channel may be expressed as thefollowing Equation (4) (1≤m≤M).

$\begin{matrix}{P_{m} = \left\{ \begin{matrix}{{0{for}m} = {{{CQI}{index}} + 1}} \\{\frac{\gamma}{{❘h_{B}❘}^{2}}{otherwise}}\end{matrix} \right.} & \left\lbrack {{Equation}4} \right\rbrack\end{matrix}$

In some example embodiments, as described above with reference to FIG.8A, a CQI index may be encoded based on unary coding, and in a casewhere the magnitude P of the first transmission power level iscalculated as in Equation (2), the transmission power level P_(m) of them^(th) resource R_(m) in the feedback channel may be expressed as thefollowing Equation (5) (1≤m≤M).

$\begin{matrix}{P_{m} = \left\{ \begin{matrix}{{\frac{\gamma}{{❘h_{B}❘}^{2}}{for}1} \leq m \leq {{{CQI}{index}} + 1}} \\{0{otherwise}}\end{matrix} \right.} & \left\lbrack {{Equation}5} \right\rbrack\end{matrix}$

In some example embodiments, as described above with reference to FIG.8B, a CQI index may be encoded based on unary coding, and in a casewhere the magnitude P of the first transmission power level iscalculated as in Equation (2), the transmission power level P_(m) of them^(th) resource R_(m) in the feedback channel may be expressed as thefollowing Equation (6) (1≤m≤M).

$\begin{matrix}{P_{m} = \left\{ \begin{matrix}{{0{for}1} \leq m \leq {{{CQI}{index}} + 1}} \\{\frac{\gamma}{{❘h_{B}❘}^{2}}{otherwise}}\end{matrix} \right.} & \left\lbrack {{Equation}6} \right\rbrack\end{matrix}$

In a case where the magnitude P of the first transmission power level iscalculated as in Equation (2), reception power Q_(m), accumulated in them^(th) resource R_(m), of the base station 22 in the feedback channel,may be expressed as the following Equation (7) (1≤m≤M).

Q _(m)=Σ_(i∈L) |h _(B)|² P _(m) ^(i) +N=Σ _(i∈L) γ+N≈γ|L|  [Equation 7]

In Equation (7), L may denote a set of terminals which outputtransmission power having the first transmission power level in them^(th) resource R_(m), P_(m) ^(i) may denote transmission power of them^(th) resource R_(m) output from an i^(th) terminal, and N may denoteadditive white Gaussian noise (AWGN). Examples of an operation ofdetermining, by using the base station 22, a lowest channel conditionbased on accumulated reception power of resources in the feedbackchannel will be described below with reference to FIGS. 11A, 11B, 12A,and 12B.

FIGS. 11A and 11B are graphs showing examples of combined channelfeedback obtained by a base station according to an example embodiment.In detail, as described above with reference to FIG. 7A, the graph ofFIG. 11A shows an example of combined channel feedback from channelfeedbacks generated based on one-hot encoding, and as described abovewith reference to FIG. 7B, the graph of FIG. 11B shows an example ofcombined channel feedback from channel feedbacks generated based onone-cold encoding. The combined channel feedback of FIG. 11A and thecombined channel feedback of FIG. 11B may be processed by the basestation 12 of FIG. 1 . Hereinafter, FIGS. 11A and 11B will be describedwith reference to FIG. 1 .

Referring to FIG. 11A, the base station 12 may determine a location of aresource corresponding to a lowest channel condition from amongresources having a reception power level which is higher than a firstthreshold value THR1 and may determine transmission parameters based onthe determined location of the resource. For example, when channelfeedbacks generated by the first to p^(th) terminals 14_1 to 14_p basedon one-hot encoding are accumulated as illustrated in FIG. 11A, thesecond resource R2 may be detected, and thus, the base station 12 maydetermine the transmission parameters based on feedback informationcorresponding to the second resource R2. That is, when the receptionpower Q_(m) accumulated in the m^(th) resource R_(m) is expressed asEquation (7) (1≤m≤M), an index m* of a resource recognized by the basestation 12 may be expressed as the following Equation (8).

m*=min {m|Q _(m) >THR1, 1≤m≤M}  [Equation 8]

When the second transmission power level (or reception power of the basestation 12 corresponding to the second transmission power level) iszero, the first threshold value THR1 may be greater than zero and lessthan γ.

Referring to FIG. 11B, the base station 12 may determine a location of aresource corresponding to a lowest channel condition from amongresources having a reception power level which is lower than a secondthreshold value THR2 and may determine transmission parameters based onthe determined location of the resource. For example, when channelfeedbacks generated by the first to p^(th) terminals 14_1 to 14_p basedon one-cold encoding are accumulated as illustrated in FIG. 11B, thesecond resource R2 may be detected, and thus, the base station 12 maydetermine the transmission parameters based on feedback informationcorresponding to the second resource R2. That is, when the receptionpower Q_(m) accumulated in the m^(th) resource R_(m) is expressed asEquation (7) (1≤m≤M), an index m* of a resource recognized by the basestation 12 may be expressed as the following Equation (9).

m*=min {m|Q _(m) <THR2, 1≤m≤M}  [Equation 9]

When the second transmission power level (or reception power of the basestation 12 corresponding to the second transmission power level) iszero, the second threshold value THR2 may be less than pγ, which is amaximum reception power level (i.e., a reception power levelcorresponding to reception power into which transmission power havingfirst transmission power levels of the first to p^(th) terminals 14_1 to14_p are all accumulated), and greater than (p−1)γ.

FIGS. 12A and 12B are graphs showing examples of combined channelfeedback obtained by a base station according to an example embodiment.In detail, the graph of FIG. 12A shows an example of combined channelfeedback from channel feedback generated based on unary coding describedabove with reference to FIG. 8A, and the graph of FIG. 12B shows anexample of combined channel feedback from channel feedbacks generatedbased on unary coding described above with reference to FIG. 8B. Thecombined channel feedback of FIG. 12A and the combined channel feedbackof FIG. 12B may be processed by the base station 12 of FIG. 1 .Hereinafter, FIGS. 12A and 12B will be described with reference to FIG.1 .

Referring to FIG. 12A, the base station 12 may determine a location of aresource corresponding to a best channel condition (i.e., a channelcondition corresponding to a best channel) from among resources having areception power level which is higher than a third threshold value THR3and may determine transmission parameters based on the determinedlocation of the resource. For example, when channel feedbacks generatedby the first to p^(th) terminals 14_1 to 14_p based on unary coding ofFIG. 8A are accumulated as illustrated in FIG. 12A, the second resourceR2 may be detected, and thus, the base station 12 may determine thetransmission parameters based on feedback information corresponding tothe second resource R2. That is, when the reception power Q_(m)accumulated in the m^(th) resource R_(m) is expressed as Equation (7)(1≤m≤M), an index m* of a resource recognized by the base station 12 maybe expressed as the following Equation (10).

m*=max {m|Q _(m) >THR3, 1≤m≤M}  [Equation 10]

Similarly to the second threshold value THR2 of FIG. 11B, when thesecond transmission power level (or reception power of the base station12 corresponding to the second transmission power level) is zero, thethird threshold value THR3 may be less than pγ, which is a maximumreception power level (i.e., a reception power level corresponding toreception power into which transmission power having first transmissionpower levels of the first to p^(th) terminals 14_1 to 14_p are allaccumulated), and greater than (p−1)γ.

Referring to FIG. 12B, the base station 12 may determine a location of aresource corresponding to a best channel condition from among resourceshaving a reception power level which is lower than a fourth thresholdvalue THR4 and may determine transmission parameters based on thedetermined location of the resource. For example, when channel feedbacksgenerated by the first to p^(th) terminals 14_1 to 14_p based on unarycoding of FIG. 8B are accumulated as illustrated in FIG. 12B, the secondresource R2 may be detected, and thus, the base station 12 may determinethe transmission parameters based on feedback information correspondingto the second resource R2. That is, when the reception power Q_(m)accumulated in the m^(th) resource R_(m) is expressed as Equation (7)(1≤m≤M), an index m* of a resource recognized by the base station 12 maybe expressed as the following Equation (11).

m*=max {m|Q _(m) <THR4, 1≤m≤M}  [Equation 11]

Similarly to the first threshold value THR1 of FIG. 11A, when the secondtransmission power level (or reception power of the base station 12corresponding to the second transmission power level) is zero, thefourth threshold value THR4 may be greater than zero and less than γ.

FIG. 13 is a diagram illustrating a wireless communication system 130according to an example embodiment. As illustrated in FIG. 13 , thewireless communication system 130 may include a base station 132 andfirst to q^(th) multicast groups 134_1 to 134_q (where q is an integerof more than 0).

As described above with reference to the drawings, terminals included inthe same multicast group may share a feedback channel and may transmitchannel feedbacks on the feedback channel, and thus, the base station132 may receive combined channel feedback on the feedback channel. Forexample, as illustrated in FIG. 13 , a plurality of terminals includedin the first multicast group 134_1 may provide first combined channelfeedback CFs_1 to the base station 132 and may receive first multicasttransmission MC_1 from the base station 132. A plurality of terminalsincluded in the second multicast group 134_2 may provide second combinedchannel feedback CFs_2 to the base station 132 and may receive secondmulticast transmission MC_2 from the base station 132. Also, a pluralityof terminals included in the q^(th) multicast group 134_q may provideq^(th) combined channel feedback CFs_q to the base station 132 and mayreceive q^(th) multicast transmission MC_q from the base station 132.

The feedback channel may be shared by terminals included in the samemulticast group and may differ from a feedback channel of anothermulticast group. To this end, the base station 132 may respectivelyallocate a plurality of different feedback channels to a plurality ofmulticast groups. For example, the base station 132 may respectivelyallocate q different feedback channels to the first to q^(th) multicastgroups 134_1 to 134_q, for receiving first to q^(th) combined channelfeedbacks CFs_1 to CFs_q. Examples of feedback channels capable of beingallocated by the base station 132 will be described below with referenceto FIG. 14 .

FIG. 14 is a diagram illustrating a physical time-frequency structurefor feedback channels according to an example embodiment. As describedabove with reference to FIG. 13 , the base station 132 may respectivelyallocate q different feedback channels to the first to q^(th) multicastgroups 134_1 to 134_q. Hereinafter, FIG. 14 will be described withreference to FIG. 13 .

Referring to FIG. 14 , a feedback channel resource FC_R may include aplurality of feedback channels FC₁₁ to FC_(XY) capable of allocation(where each X and Y is an integer of more than 1). The base station 132may allocate a feedback channel, unallocated to another multicast group,of the plurality of feedback channels FC₁₁ to FC_(XY) to each of thefirst to q^(th) multicast groups 134_1 to 134_q. Subsequently, asdescribed above with reference to FIG. 2 , the base station 132 maytransmit allocation information about a feedback channel to each of thefirst to q^(th) multicast groups 134_1 to 134_q. As described above withreference to FIGS. 3A and 3B, each of the feedback channels FC₁₁ toFC_(XY) may include M resources divided in a time domain or a frequencydomain.

In some example embodiments, the base station 132 may allocate two ormore feedback channels to one multicast group. For example, when thenumber of multicast groups is small, the base station 132 may allocatetwo or more adjacent feedback channels to a multicast group including aplurality of terminals. Therefore, terminals included in a multicastgroup with two or more adjacent feedback channels allocated thereto maydetermine the same transmission power level for two or more successiveresources, and thus, the base station 132 may obtain feedbackinformation from combined channel feedback at high accuracy.

FIG. 15 is a block diagram illustrating a wireless communicationapparatus 150 according to an example embodiment. The wirelesscommunication apparatus 150 may be an example of each of a base station(for example 12 of FIG. 1 ) and a terminal (for example, 14_1 of FIG. 1). As illustrated in FIG. 15 , the wireless communication apparatus 150may include an antenna module 152, a transceiver 154, a signal processor156, and a main processor 158.

The antenna module 152 may include a plurality of antennas, for spatialdiversity, polarization diversity, and spatial multiplexing. Thetransceiver 154 may process a transmission signal TX provided from thesignal processor 156 to output a radio frequency (RF) signal to theantenna module 152 and may process an RF signal received through theantenna module 152 to provide a reception signal RX to the signalprocessor 156. In some example embodiments, the transceiver 154 mayinclude a low noise amplifier, a mixer, a filter, and a power amplifierand may be referred to as a radio frequency integrated circuit (RFIC).

The signal processor 156 may generate the transmission signal TX from apayload PL provided by the main processor 158 and may generate thepayload PL from the reception signal RX to provide the generated payloadPL to the main processor 158. The signal processor 156 may performoperations of forming a communication channel along with anotherwireless communication apparatus based on a wireless communicationsystem including the wireless communication apparatus 150. In someexample embodiments, the signal processor 156 may be referred to as acommunication processor, a baseband processor, and a modem. The mainprocessor 158 may generate the payload PL including information which isto be provided to the other wireless communication apparatus, mayprovide the generated payload PL to the signal processor 156, and mayreceive the payload PL, including information provided by the otherwireless communication apparatus, from the signal processor 156.

The signal processor 156 may perform a method of receiving multicasttransmission described above with reference to the drawings. Forexample, the signal processor 156 may be implemented using processingcircuitry such as hardware including logic circuits, a hardware/softwarecombination such as a processor executing software; or a combinationthereof. For example, while the processing circuitry is illustrated asbeing a CPU, the processing circuitry may include, but is not limitedto, a CPU, an arithmetic logic unit (ALU), a digital signal processor, amicrocomputer, a field programmable gate array (FPGA), a System-on-Chip(SoC) a programmable logic unit, a microprocessor, or anapplication-specific integrated circuit (ASIC), etc. The processingcircuitry may be configured as a special purpose computer tosimultaneously obtain a plurality of channel conditions, used fordetermination of transmission parameters in the multicast/broadcastservice, on a feedback channel shared by a plurality of terminals,instead of obtaining the channel conditions from the plurality ofterminals and may obtain a worst channel condition (i.e., a lowestchannel condition). The processing circuitry may improve the functioningof the wireless communication system 10 itself by determiningtransmission parameters for multicast transmission MC within a certaintime regardless of a variation of the number of terminals included in amulticast group 14, which receives the multicast transmission MC, thusenhancing the efficiency of the multicast/broadcast service.

More specifically, in some example embodiments, the signal processor 156may perform operations performed by the base station for the multicasttransmission. For example, the signal processor 156 may performoperations including operation S10, operation S20, operation S60, andoperation S70 of FIG. 2 . Also, in some example embodiments, the signalprocessor 156 may perform operations performed by the terminal for themulticast transmission. For example, the signal processor 156 mayperform operations including operation S30, operation S40, and operationS50 of FIG. 2 . An example of the signal processor 156 will be describedbelow with reference to FIG. 16 .

FIG. 16 is a block diagram illustrating a signal processor 160 accordingto an example embodiment.

Referring to FIG. 16 , the signal processor 160 may include anapplication specific integrated circuit (ASIC) 162, an applicationspecific instruction set processor (ASIP) 164, and a memory 166. TheASIC 162, the ASIP 164, and the memory 166 may communicate with oneanother, and in some example embodiments, may be connected to a bus.Also, at least two of the ASIC 162, the ASIP 164, and the memory 166 maybe embedded into a single chip.

The ASIC 162 may include a plurality of function blocks (for example,hardware intellectual properties (IPs) and hardware accelerators) in anintegrated circuit designed by a logic combination. The function blocksincluded in the ASIC 162 may include at least some of operations in themethod for multicast transmission described above with reference to thedrawings. The ASIC 162 may obtain data, needed for performing anoperation, from the memory 166, and after performing an operation, theASIC 162 may store result data in the memory 166.

The ASIP 164, an integrated circuit customized for the specific purpose,may support a dedicated instruction set for a certain application andmay execute instructions in the instruction set. The ASIP 164 maycommunicate with the memory 166 and may execute a plurality ofinstructions stored in the memory 166 to perform at least some of theoperations in the method for multicast transmission described above withreference to the drawings.

The memory 166, a non-transitory storage device, may communicate withthe ASIP 164 and may store the plurality of instructions executed by theASIP 164. For example, in a non-limiting embodiment, the memory 166 mayinclude an arbitrary-type memory accessible by the ASIP 164 like randomaccess memory (RAM), read only memory (ROM), tape, a magnetic disk, anoptical disk, a volatile memory, a non-volatile memory, and acombination thereof.

While example embodiments of the inventive concepts have beenparticularly shown and described with reference to example embodimentsthereof, it will be understood that various changes in form and detailsmay be made therein without departing from the spirit and scope of thefollowing claims.

What is claimed is:
 1. A method performed by a terminal to communicate with a base station, the method comprising: receiving allocation information about a feedback channel including a plurality of resources; generating feedback information based on an estimated channel between the terminal and the base station; and transmitting a channel feedback on the feedback channel based on the feedback information, wherein the channel feedback corresponds to a plurality of transmission power levels of the plurality of resources.
 2. The method of claim 1, further comprising: generating a bit string including a plurality of bits based on the feedback information, the plurality of bits respectively corresponding the plurality of resources, wherein the transmitting a channel feedback comprises controlling the plurality of transmission power levels based on the bit string.
 3. The method of claim 2, wherein the generating a bit string comprises: encoding the feedback information to the bit string based on an encoding scheme.
 4. The method of claim 3, wherein the generating a bit string further comprises: extracting the encoding scheme from the allocation information.
 5. The method of claim 3, wherein the encoding scheme is one of one-hot encoding, one-cold encoding and unary coding.
 6. The method of claim 1, wherein the feedback information includes at least one of channel-status information (CSI), channel quality indication (CQI), a modulation coding scheme (MCS), a rank indicator (RI) and precoder matrix indication (PMI).
 7. The method of claim 1, wherein the plurality of resources are continuously disposed in a time domain and each have a constant width in a frequency domain.
 8. The method of claim 1, wherein the plurality of resources are continuously disposed in a frequency domain and each have a constant width in a time domain.
 9. A method performed by a terminal to communicate with a base station, the method comprising: receiving allocation information associated with a feedback channel including a plurality of resources; generating feedback information based on an estimated channel between the terminal and the base station; and transmitting a channel feedback on the feedback channel based on the feedback information, wherein the transmitting a channel feedback comprises controlling each of a plurality of transmission power levels of the plurality of resources based on the feedback information.
 10. The method of claim 9, wherein the controlling the plurality of transmission power levels comprises: setting each of the plurality of transmission power levels to a first level or a second level based on the feedback information.
 11. The method of claim 10, further comprising: determining at least one of a magnitude of the first level and a magnitude of the second level based on the estimated channel.
 12. The method of claim 9, wherein the feedback information includes at least one of channel-status information (CSI), channel quality indication (CQI), a modulation coding scheme (MCS), a rank indicator (RI) and precoder matrix indication (PMI).
 13. The method of claim 9, wherein the plurality of resources are continuously disposed in a time domain and each have a constant width in a frequency domain.
 14. The method of claim 9, wherein the plurality of resources are continuously disposed in a frequency domain and each have a constant width in a time domain.
 15. A method performed by a base stating to communicate with a plurality of terminals, the method comprising: transmitting allocation information about a feedback channel to the plurality of terminals, the feedback channel including a plurality of resources shared by the plurality of terminals; receiving a plurality of channel feedbacks on the feedback channel from the plurality of terminals; detecting a plurality of reception power levels respectively corresponding to the plurality of resources; determining a worst channel condition based on the plurality of reception power levels; and providing multicast transmission to the plurality of terminals based on the worst channel condition.
 16. The method of claim 15, wherein the determining the worst channel condition comprises: detecting, among the plurality of resources, at least one resource corresponding to a reception power level that is higher than a first threshold; detecting a resource having a lowest index or a highest index among the at least one resource; and determining the worst channel condition based on the lowest index or the highest index.
 17. The method of claim 15, wherein the determining the worst channel condition comprises: detecting, among the plurality of resources, at least one resource corresponding to a reception power level that is lower than a second threshold; detecting a resource having a lowest index or a highest index among the at least one resource; and determining the worst channel condition based on the lowest index or the highest index.
 18. The method of claim 15, wherein the determining the worst channel condition comprises determining at least one of channel-status information (CSI), channel quality indication (CQI), a modulation coding scheme (MCS), a rank indicator (RI) and precoder matrix indication (PMI).
 19. The method of claim 15, wherein the plurality of resources are continuously disposed in a time domain and each have a constant width in a frequency domain.
 20. The method of claim 15, wherein the plurality of resources are continuously disposed in a frequency domain and each have a constant width in a time domain. 